Repeatedly executing a query in psql

Sometimes, we want to execute a query more than once, repeated at regular intervals; in this recipe, we will look at an interesting psql command that does exactly that.

How to do it…

The \watch meta-command allows psql users to automatically (and continuously) re-execute a query.

This behavior is similar to the watch utility of some Linux and Unix environments.

In the following example, we will run a simple query on pg_stat_activity and ask psql to repeat it every 5 seconds. You can exit at any time by pressing Ctrl + C:

gabriele=> SELECT count(*) FROM pg_stat_activity;
 count
-------
     1
(1 row)

gabriele=> \watch 5
Watch every 5s     Tue Aug 27 21:47:24 2013

 count
----...